The Tuscan bank, the world's oldest still in business, needs to raise more than seven times its market value in cash in order to sell bad loans and boost capital after industry stress tests in July singled it out as Europe's weakest.

New Chief Executive Marco Morelli told shareholders he had showcased the bank's rescue plan to more than 250 investors, including hedge funds and sovereign wealth funds, in the 70 days since taking office, but had failed to obtain any firm backing.

Weighing on investors' mind is a constitutional referendum on Dec. 4 which could topple Italy's reformist government and usher in a period of political instability.

The Monte dei Paschi banking foundation - which used to control the bank and now owns just 0.7 percent of it - said on Thursday it would like to wait until after the vote before deciding whether to invest further in Monte dei Paschi.

Morelli, the former head of Bank of America Merrill Lynch in Italy, is aiming to raise the money this year to cover losses from the planned sale of 28 billion euros in gross bad loans.

The CEO told reporters a window existed for the capital increase to start around December 7-8 and to close before the Christmas holidays.

If the plan falls through, Monte dei Paschi would need state support to survive.

Under tougher new European Union rules on bank bailouts, public aid can only come after hitting investors first.

Hundreds of ordinary Italians have already lost their savings in a string of bank crises following a deep recession that saddled lenders with 356 billion euros in soured debts.

Around 150,000 small shareholders hold 55 percent of Monte dei Paschi's capital. Italy's Treasury is the top investor with a 4 percent stake it received as payment for lending the bank money during the financial crisis.